An arc furnace for use with direct current requires an electric connection with the melt in the furnace's hearth to provide the circuit required for an arc or arcs formed between the melt and one or more electrodes having lower ends spaced above the melt's surface.
A hearth made of conventional refractory is electrically non-conductive and requires one or more electrical connectors to be projected through the hearth to contact the melt in the hearth. Without water cooling such a connector has an undesirable short service life. Water cooling has been avoided as much as possible because it is considered to be dangerous if used close enough to the inner end of the connector to have any practical effect. For example, if during the operation of a furnace the melt burns through the hearth and reaches water, an explosion may result. A cathodic graphite arcing electrode has better operating and service life characteristics then one operated as an anode. If the arcing circuit is completed by using two arcs with the circuit closed by the melt via the arcs, one electrode must operate as an anode, which is undesirable.